DK2163887T3 - Method and circuit arrangement for the measurement of physical parameters of the fluids and their uses - Google Patents

Description

The present invention relates to a method and circuit arrangement for measuring the quality change of oils used for lubrication or insulation, for measuring parameters of crude oils and their by-products, and for measuring impedance components for electrically conductive or electrically non-conductive fluids, their realization and their application. In particular, the specific electrical conductivity and dielectric coefficient are measured. Due to their temperature dependencies, further oil temperature is measured. Both abrasive components, uprooted oil molecules, soiling and mechanical soiling, salts, acids, water, oil soaps which are formed, etc., increase electrical conductivity. Based on the fact that the electrical conductivity of oil is substantially inferior to the conductivity of the soiling components, there is a direct correlation between the electrical conductivity and the degree of soiling. The change in the degree of dirt further shows the current wear or degree of dirt, respectively. the composition of crude oils and their by-products. Examples of applications are the monitoring of gear oils, hydraulic oils, transformers, engine oils, monitoring of crude oil production and reprocessing, etc.

Conceptually comparable measurements have been established in connection with water conductivity measurement. In this context, the electrical conductivity is in any case several tier potentials larger and consequently much easier to measure. Also in the water measurement, the electrical conductivity is a sump parameter for the ion concentration and / or soiling. In any case, with the sensing system according to the invention, the supplementary dielectric coefficient is measured, preferably for moisture measurement, water content determination, for detecting the degradation of additives and / or for measuring gas components.

The prior art is particularly reproduced in the patent specification DE 196 28 690. The method for measuring the electrical conductivity and the dielectric coefficient described by means of clock-controlled DC voltages or clock-controlled DC currents as measuring signals and the characteristics described in the patent has proved extremely advantageous in use. One disadvantage of the electronic method, however, is that '' the integration at each change of the test signal (flanks) is reset ''. Also, when opening the analog switch, a charge injection (Charge Injection) occurs which falsifies the measurement result. To measure the conductivity and the dielectric coefficient, two sensors are required or the sensor electronics must be switched. Furthermore, the sensor electronics are relatively complex and contain additional sources of error. The mechanical realization of the base sensor is also very troublesome. A further disadvantage is that with the described sensor concept, the oil parameters to be measured, and thus ultimately also the oil quality, cannot be measured in the actual lubrication gap.

The patent application DE 10217383 from Siemens AG with the theme "Zylinderkopfintegriertes Dieseleinspritzsystem mit Olsensor" deals with injectors which are fully integrated into the cylinder head of a fuel driven machine. In the application, an oil sensor is provided for detecting the quality of the engine oil and its oil filling state. It is further stated: "Pre-welding is obtained from the Olsensor with the Quality and / or the Fill rate of the Motorols using a dielectric constant of the Motorols." The patent DE 199 63 204 from the company Cummins Inc. Columbus, Ind., US, discloses a method for determining the residual life and / or residual useful life of engine oil in an engine where engine parameters such as soot concentration and / or viscosity of the engine oil are measured.

The solutions proposed in the cited patents have the disadvantages of cumbersome base sensors and sensor electronics. Furthermore, their measurement accuracy is not optimal.

It is an object of the invention to realize basic sensors which are of high accuracy and yet can be realized simply and cost-effectively, and to realize sensor electronics for measuring quality changes for oils, machines, transformers, turbines, compressors, motors etc. and their use, in particular for the indication of preventive maintenance measures, inadmissible operating conditions, high loads, etc., long before a preventive repair, as well as for quality assessment and for condition monitoring. With the sensor system according to the invention it should also be possible to measure immediately in the lubrication slot. The oil sensing system according to the invention enables a state-oriented, preventive maintenance of machines, transformers, turbines, compressors, motors, etc. The interdisciplinary arrangement of a quantified assessment of the change of the system oil gear, oil engine etc., via the moments measured with the sensing system according to the invention oil soiling and its temporal change, enables an assessment of the gear, motor, transformer wear, etc. and of the oil wear. Preventive maintenance measures can be indicated long before a preventive repair.

A further application of the sensor system according to the invention is the measurement of crude oils produced and their by-products and / or the composition of crude oil products. In particular, sump parameters for salts, acids, ion concentrations, water content and gases in crude oil or crude oil products are measured.

The electrical conductivity and the dielectric coefficient of the oil are measured independently of each other. The fine soiling of the oil, such as wear, broken oil molecules, the formation of soaps, etc., is especially pronounced by an increase in the electrical conductivity. To measure the breakdown of additives and to determine the water content, the supplementary dielectric coefficient of the oil is measured. In order to avoid polarization effects, mean-free alternate sizes are used as measurement signals. The invention also encompasses the development of an electronic measurement method with clock controlled, mean-free measurement signals for separately measuring the resistance and capacity of the base sensor. According to the invention, the base sensor resistance Rx and the base sensor capacity Cx are determined by a measuring signal. From this, the conductivity and the dielectric coefficient are calculated. The electrical conductivity κ and the dielectric coefficient are temperature dependent, as the temperature coefficients are less dependent on the oil, but in particular also dependent on the oil soiling, the sensor geometry further changes depending on the temperature. A self-learning adaptive temperature compensation, respectively. a conversion to a reference temperature are also components of the invention. Figure 1 shows an object grid for an exemplary embodiment of the oil sensing system.

The object network consists of rectangularly displayed functional units, the so-called objects, and circularly displayed data space. Objects are function units with autonomy and defined power. They are characterized by inputs and feedback-free outputs. Objects communicate with each other via the data spaces shown as circles. Data reception is characterized by arrows between data rooms and objects. An object network illustrates the data flow through a system. It allows a static interpretation of the range of entry for individual functional units. Objects and object networks can be refined step by step. Examples of objects are hardware components, software programs, sensors, processors, automation systems, or even users of a measurement system. For example, data rooms are: signals on wires, workstations, measurement signals, screens or prints.

A basic sensor construction according to the invention is described below. Figure 2 shows an overview sketch of a construction variant of the realized sensor system.

The active base sensor part here consists of two or more base sensor plates 1 with the surface A, which, at a constant spacing 1, are attached to the metal pins in a glass / metal passage 2. The plates for the base sensor are placed in the middle of the measuring chamber, so that a favorable and direction-independent influx of the flowing media is ensured. A special orientation of the sensor housing parts is not required in this construction. The materials for the sensor housing and the pins in the glass / metal feedthrough 2, with respect to their expansion properties, are precisely adapted to the machined glass in the feed. Figure 3 shows the glass / metal lead-in 2 in the sensor housing, Figure 4 shows a basic sensor arrangement with three electrode plates 9.

The conductivity of electrically insulating structural elements and the conductivity of insulation in electrical passages are of the same order of magnitude as the electrical conductivity of the pure oil to be measured. However, the conductivity of the bushings and the support materials should not be included in the measurement result. This object is achieved in connection with the precise sensor electronics in accordance with the invention. To this end, the test signal, preferably a sectional constant voltage or a sectional constant current, is coupled to a sensor electrode, the second electrode plate according to the invention being coupled to the inverting input of a, preferably on a virtual frame, current-switched operational amplifier. Alternatively, the coupling to the inverting input is on a voltage-coupled operational amplifier.

An alternative embodiment is the immediate screw-in of an arrangement according to picture 4 in a pipe wall, for example a crude oil pipeline.

An alternative basic sensor realization is a flat electrode arrangement. It is preferably manufactured as a gold-platinum alloy on ceramic substrate. The preparation method is similar to the thick film hybrid technique. The electrode concept and a correspondingly realized electrode arrangement are shown in Figure 5.

The two comb-shaped electrodes 10, 11 correspond in their basic function to the two capacitor plates, on the middle electrode 12 the electronics frame or a suitable shielding signal is coupled.

Figure 6 shows a simplified electrical equivalence diagram for the base sensor as a network of an R-C combination between the electrode plates.

Assuming a homogeneous field, the equipotential lines are within the capacitor parallel to the electrodes. Consequently, over the transverse branches there is no flow that can be omitted.

To avoid polarization effects, the base sensor arrangement is associated with mean-free AC voltage signals. In this connection, a measurement with sinusoidal AC voltage is less suitable, since the capacitive current would be substantially larger than the ohmic component of the current and thus the current components could only be separated with significant electronics difficulty.

Accordingly, for the conductivity measurement, the electrodes are applied to a sectional constant voltage. In the flipped state, no current is flowing through the capacitors in the equivalence diagram in time sections with constant input voltage. During the conductivity measurement, there is a constant voltage on the electrodes. Accordingly, in the DC equivalence diagram, the additional capacitors can be omitted. From the series and parallel coupling, the resulting equivalence resistor R is obtained. From this, with knowledge of the geometry of the electrode arrangement, respectively. the cell constant kz, the conductivity κ determined.

For the case of a constant electric field strength E between the electrodes, the sensor resistance is:

and with the cell constant

the electrical conductivity

The quotient j is the cell constant. It depends solely on the geometry of the sensor arrangement.

Wear, ions, broken oil molecules, acids, oil soaps, etc. increase the conductivity κ of the oil. The electrical conductivity increases with increasing ion concentration and ion mobility. The electrical conductivity of virtually all soiling products is high in comparison to the extremely poor conductivity of pure oil. There is a direct correlation between the electrical conductivity and the degree of soiling of the oil. An increase in the electrical conductivity of oils during operation can be interpreted as increasing oil soiling or greater oil wear. Due to oil quality changes respectively. thus, ions and foreign particles generated, individual branches in the equivalence diagram are partially shorted and the measured electrical conductivity and the measured dielectric constant changed. According to the invention, the measurement of the dielectric constant can be carried out via the same basic sensor arrangements and sensor electronics, through which the electrical conductivity is also determined.

The capacity Cx becomes via the definition equation for the capacity

calculated. The capacity is the shear flow between two electrodes divided by the voltage between the electrodes.

At spatially constant electric field strength E this can again be pulled out in front of the integral and shortened:

respectively.

The quotient j is again the cell constant kz. The capacity is (at a constant dielectric coefficient) determined only by the geometric shape of the capacitor and the dielectric material properties.

The dielectric coefficient for oils is on the order of «2.2, the dielectric coefficient for water is approximately is ~ 81. The water content of oil can be measured by the measurement of the dielectric coefficient. In the case of oils used as a cooling lubricant, due to the oil wear increased with increasing water content, the water content of the oil must be additionally measured via an accurate measurement of the dielectric coefficient. Further, with this information, the influence of water on the conductivity change in the oil can be compensated. In other applications, the measured dielectric coefficient allows an opinion on the decomposition of additives in oil.

After applying a higher frequency alternating voltage to the electrodes, the current flowing through the capacitors in the equivalence diagram is substantially greater than the current via the high impedance resistors of the oil. As a simplified AC voltage diagram, the equivalence diagram outlined in Figure 7 can be assumed.

The individual capacitors can again be summed up to a common capacity C. With knowledge of the sensor geometry respectively. the cell constant kz is thereby determined the dielectric coefficient sought.

The base sensor is an electrode arrangement in which the oil to be measured acts as an electrical conductor for conductivity measurement and for dielectric constant measurement as a dielectric. Oil is an electrical non-conductor. The extreme high impedance of the base sensor and the resulting extremely low measuring currents condition a high interference sensitivity with radiated electromagnetic fields. By integrating the extremely small current, a sufficient disturbance suppression is obtained.

Resistance and capacity must be measured independently. To avoid polarization effects, the base sensor is applied to a mean-free test signal. Otherwise, additional polarization voltages would falsify the measurement result or even make measurement impossible. The use of sinusoidal test signals, due to the extremely high impedance resistance Rx and the low ohmic current component relative to the capacitive shear currents via the sensing capacity Cx, is problematic. Accordingly, the capacity and resistance of the base sensor must be measured with clock-controlled, mean-free, section-constant test signals. For this, the electrodes are applied to a section constant voltage and the resulting electric current is measured. In order to achieve a high disturbance suppression and thus also a high accuracy, the current is integrated over time and evaluated for conductivity measurement.

Consequently, the high impedance base sensor requires an extremely sensitive and yet highly interference-resistant electronics. Both can be achieved by means of an integrating measurement electronics and an immediate transformation of the measurement information into digital signals. For this, the base sensor resistance and the base sensor capacity via operational amplifier circuits (OPs) are converted to frequency respectively. time signals. The time measurement is done via a microcontroller, which further takes over the digital signal processing.

The analog sensor electronics (see Figure 8) consist of a relaxation oscillator, the base sensor being connected to the integrator's input circuit. From the analog output signal from the integrator, via a microcontroller, both the electrical conductivity and also the dielectric coefficient are determined. For this, the searched measurement-size proportional time intervals for the sensor signal are measured. In this connection, a minimum residual conductivity Kmin, which must be further determined, must be exceeded.

The output signals of the integrator u ,, the two Schmitt triggers uaxi and uaX2, the lower Schmitt trigger act as comparator, are outlined in Figure 9.

The output voltages from the two Schmitt triggers are applied to an XOR gate. Its output signal contains the peak termed TK, which is proportional to the specific resistance p and inversely proportional to the electrical conductivity:

The differences between TK and T2 are proportional to the dielectric coefficient:

In the following, these two equations are explained. Sometimes TK, the electrical conductivity of the oil is measured. The input voltage of the integrator and thus also the voltage across the sensor capacity Cx is constant during this time interval. This results in an almost constant capacity for a period of time

Thus, for the integrator output voltage ui follows the switching time of the Schmitt trigger

and for UaXi = const.

Detection of the zero throughput of the integrator output voltage is done via the one shown at the bottom of the circuit diagram, as Schmitt trigger with very little hysteresis coupled comparator. The switching point of the Schmitt trigger is given by

Inserted into the equation above is obtained

or for conductivity:

Due to the parallel capacity Cx in the sensor, a jump in the integrator output voltage is caused. From this, the dielectric coefficient is determined.

Figure 10 shows the relationship between TK and Τε.

For calculation, one needs the time Τε. This corresponds to the integration time of the integration over the jump height USp caused by Cx. It can be calculated from the difference between the times TK and T2.

Times TK and T2 are provided in the sensor electronics by means of the XOR gate coupled to the analog sensor electronics (see Figure 10). TK is then high-time and T2 is low-time of the output voltage on the XOR gate. At the time of switching the output voltage from the Schmitt trigger and thus also the input voltage on the integrator, the two capacitors Cx and C are recharged. They form a capacitive voltage divider, which can be described by the equation

From the equation of the output voltage from the integrator follows

and

follows

respectively.

From this, the dielectric coefficient is calculated from the conductivity κ and the time Τε.

By means of the sensor electronics, the electrical conductivity as well as the dielectric coefficient of the oil are determined from the one sensor signal. In any case, a minimum conductivity is also required for the measurement of the dielectric coefficient. In a special design of the electronics, a very high conductivity is simulated, by means of a very high impedance resistance coupled in parallel with the base sensor connection. From the measured conductivity, the simulated conductivity is then subtracted again.

To compensate for manufacturing tolerances for the base sensor, its calibration can be done by measuring the capacity of the base sensor filled with high-dried air or high-purity nitrogen. Thus, effects of mechanical manufacturing tolerances on the measurement result can be eliminated. Since the electronics circuit described above requires a minimum conductivity, either a minimum conductivity is simulated via the high impedance resistors coupled to the base sensor or a modified electronics circuit is used in which the integration capacity C is replaced by the base sensor, in the integrator feedback branch.

Figure 11 clarifies the circuit with a relaxation oscillator.

While the dielectric coefficient εΓ respectively. the sensor capacity Cx in connection with the first circuit (Figure 8) is measured during the switching jump, ie at very high frequencies, the sensor capacity Cx in connection with the analog sensor electronics circuit shown in Figure 11 serves to integrate a sectional constant current. Here, the sensor capacity Cx is measured at low frequencies. Here, the parallel sensor resistance can be disregarded since the current through the capacitor is far greater than the current through Cx. One possible application by which the dielectric coefficient measurement can be used at different frequencies is fuel sensors for multifuel vessels or the characterization of different oils and / or oil components. Other applications are direct gas humidity measurement arrangements, also for aggressive gases, or gas humidity measurements with very simple electrodes, for example on the inside of vessel panes and, where appropriate, simultaneous humidity and bedding measurements.

The output voltage from the integrator is, at constant input voltage, uA and ui (0) = 0:

The Schmitt trigger built with OP2 delivers the sectional constant output voltage uAmin integrated by the inverting integrator respectively. uAmin · Achieves the integrator voltage U | trigger level of the Schmitt trigger | U | S |, the voltage ua to be integrated changes its sign. Thereby, the output of the integrator runs in the opposite direction until the second trigger level is reached.

The switching of the Schmitt trigger occurs at the switching voltages

It applies for

T is the period duration of the triangle and square oscillations and is directly proportional to the applied capacity of the base sensor and to the dielectric coefficient:

The direct measurement of the dielectric coefficient of the fluid between the two electrodes enables, in connection with the high-resolution sensor electronics, a moisture determination as well as the accurate calibration of the base sensor.

The input currents of the operational amplifiers in the analog sensor electronics circuits cause a shift in the key ratio of the output signals ua. The frequency, on the other hand, does not change. Since, according to the invention, at any one time is measured over a period or an integer multiple of a period for ua, the input rest and offset currents do not affect the measurement result. In Figure 12, the parasitic capacities of the analog sensor electronics are plotted. Figure 13 shows the same parasitic capacities in the base sensor arrangement.

Capacity CP1 is parallel to the output of the Schmitt trigger and does not adversely affect the circuit. CP2 lies parallel to the sensor capacity Cx. For reducing CP2, according to the invention, a screen is inserted, the capacity and CP2 thereby being associated with the capacities CP1 and CP3. CP3 again lies between the virtual frame of the inverting input of the operational amplifier and frame. Thus, there is no voltage across CP3, so CP3 can be ignored. Figure 14 shows the practical realization of the basic sensor. In accordance with the invention, the same shielding concept is implemented on the electronics circuit board via the insertion of ground wire paths.

To avoid polarization effects, mean-free test signals are required that the base sensor is applied to. According to the invention, rail-to-rail operational amplifiers with symmetrical supply voltage are used. An improved symmetry formation is achieved via a voltage divider with two equal resistances between the supply voltages. Its center outlet serves as a reference potential for the sensor electronics.

Through the movement of the oil acting here as an electric conductor, in the oil, due to the inevitable magnetic fields, in accordance with the law of induction, flow velocity proportional disturbance voltages are induced in the electrode arrangement. These are superimposed on the actual measurement signal. Already the constant earth magnetic field can cause this effect. Magnetic fields that change will induce additional transformer disturbance voltages, both through the flow sensors and also at the dive sensors. The sensor electronics in accordance with the invention compensate for these interference effects. The fluid movement and thus also the electrical conductivity depends on the internal friction in the oil and thus also on its temperature. Conductivity increases with oil temperature. Accordingly, an evaluation of the oil soiling requires a temperature compensation for the conductivity measurement values and a conversion to a reference temperature. For temperature compensation for the conductivity values, the additional temperature is measured, preferably via a PT100. This is preferably disposed at the electrode holders on the electronics side of the glass-metal feed-through. The conversion of the measured electrical conductivity and the dielectric coefficient according to the invention is preferably carried out via an adaptive, self-learning temperature compensation.

The calculation of the electrical conductivity and the dielectric coefficient at the reference temperature T0 can be done via a temperature dependence approximating polynomial of the form

Km is the current measurement value for the electrical conductivity at temperature T,. kTo is the approximate electrical conductivity of the oil at the reference temperature, T0, KTOa is the previously calculated (old) electrical conductivity at the reference temperature T0, a, b and c are the coefficients of the approximate polynomial to be determined adaptively,

is the temperature difference. The approximation using a third degree polynomial ensures a good approximation at acceptable low computational cost for the microprocessor used. For the determination of the coefficients of the polynomial, a risk function whose minimization allows for the determination of the coefficients sought is defined, based on the Θθΐιβ method for the least squares based on the N measurement pairs and the approximate polynomial.

Three linear independent equations are obtained for the three coefficients sought

Of these, the three coefficients sought are, for example, determined by the Cramerian rule.

In a further embodiment of the invention, if necessary, a base sensor in accordance with the invention is realized such that the volume between the electrodes is the lubricating film in a bed to be monitored. In Figure 15, such an arrangement is outlined.

Via the measured capacity C, the lubrication gap thickness 1 is determined here, if necessary.

An important complement to the oil sensing system is the addition of a suitable communication structure and the realization of a monitoring system. Areas of application for the sensor system are decentralized energy, manufacturing and automation engineering systems, such as wind turbines, transformer stations, hydraulic systems, gears, etc. For this, online monitoring of decentralized systems via a predominantly web-based monitoring system is realized. The following Figure 16 shows the object network for such a monitoring system.

The web-based, decentralized monitoring system, in which the sensor data is preferably transmitted via the Internet and entered via an embedded database into an HTML interface operated as an interface for the monitoring system, enables the monitoring of the systems by the facility user as well as service providers who are required for maintenance.

In a further embodiment of the invention, in connection with patent application DE 19914658, a measurement of the impedance spectrum of the base sensor is proposed by means of binary or ternary random pseudo-random signals. Instead of the sectional constant output signal from the Schmitt trigger in the relaxation oscillator, sectional constant digital noise signals are coupled here to the base sensor in the input branch of the integrator. The cross-correlation function θχγ (τ) of the input signal x (t) and the output signal y (t) for a linear, time invariant transfer element, here the base sensor, is equal to the folding product of the impulse response of the transmission element g (x) and the autocorrelation function φ (

or more extensively written:

This is obtained by inserting the Dahamel integral into the cross-correlation function formed by the input and output signal and switching the integration order. If the input signal is a periodic pseudo-random signal, then the integration can take place over a period of time. The impulse response of a capacitor with the capacitor current i as the input signal and the capacitor voltage u as the output signal is

The requested capacity is thus calculated via

The integral over the autocorrelation function of the pseudo-random capacitor current is known. The calculation of the cross correlation function φ / ί; (τ) between the pseudorandomic periodic capacitor current in (t) and the capacitor voltage u (t) is numerically performed by the microprocessor for each measurement. Due to the digital input signal in (t), the multiplication associated with the integration becomes a simple summation. When selecting rapidly changing input signals, the output signal can also be measured one period or a whole number of periods later. Instead of the capacity, the impulse response g (t) or, following the application of a fast Fourier transform (FFT), the transfer function of the base sensor can also be determined. In Figures 17 and 18 a realization similar to Fig. 15 is shown, but by placing the electrodes 21,22 on the tooth flank of a tooth in a gear, the oil gap 23 for the engaging model element as well as the access lines 24, 25 and the insulation 26 are made clear.

Reference number 1 Base sensor with 2 plates 2 Glass / metal / pass-through 3 Electronic circuit board 4 Sensor holder 5 Sensor head 6 Sensor cover 7 Input / output opening 8 O-ring 9 Base sensor with 3 plates 10 Camel electrode 1 11 Camel electrode 2 12 Screen electrode 13 Parasitic capacity Cpi 14 Parasitic capacity Cpi 14 Parasitic Capacity Cp3 16 Parasitic Capacity Cp2i 17 Parasitic Capacity Cp22 18 Display 19 Bearing ring 20 Roller bearing body 21 Electrode 1 22 Electrode 2 23 Oil slot 24 Electrode supply line 1 25 Electrode supply line 2 26 Insulation

Claims (17)

A method for measuring physical parameters of electrically low conductive and nonconductive fluids, wherein the fluid is between electrically conductive electrodes of a base sensor (1, 9), applying a test signal in the form of a base sensor (1, 9). a clocked DC voltage or a clocked direct current, the resulting output current or output voltage is integrated by means of an integrator whose output signal, if applicable via an amplifier, is applied to a first Schmitt trigger whose output signal is again applied as a test signal to the base sensor (1, 9); characterized in that the output signal is further applied to a second Schmitt trigger which is connected in parallel with the first Schmitt trigger and which acts as a comparator, the output of the two Schmitt triggers being coupled to an XOR gate, from whose output signals the physical parameters of the fluid to be measured are calculated by a microprocessor and fed to an evaluation logic system in which, from the measured signal, both the resistance and the capacity are determined. Method according to claim 1, characterized in that the test signal is applied in the form of clock controlled, mean-free measurement signals. Method according to claim 1 or 2, characterized in that a test signal is applied to a first sensor electrode on the base sensor (1, 9) in the form of a sectional constant voltage or a sectional constant current, and a second sensor electrode on the basis of the sensor (1). , 9) is coupled to the inverting input of an integrator designed as an operational amplifier, or alternatively to a voltage-coupled operational amplifier. A circuit arrangement for carrying out the method according to any one of claims 1 to 3, comprising a base sensor (1, 9) on which the test signal is applied on the input side and connected to the inverting input of an operational amplifier as integrator. given drop via an amplifier, the output of the integrator being connected to two parallel-coupled operational amplifiers as Schmitt triggers, the output of the first Schmitt trigger being coupled as a test signal to the base sensor (1, 9) and coupled to an XOR gate, to which is also coupled to the output of the second Schmitt trigger, the output of the XOR gate being coupled to an evaluation logic system. Use of the method and / or circuit arrangement according to any one of claims 1 to 4, characterized in that the measured electrical conductivity and / or dielectric constant and the change of the electrical conductivity and / or the change of the dielectric constant are used as a measure of an evaluation of the change of system oil-machine, oil-gear, oil-engine, oil-transformer, etc. Use according to the preamble of claim 5, characterized in that, through the measured electrical conductivity and / or dielectric constant and / or the change of the electrical conductivity and / or dielectric constant, the machine wear, gear, motor, transformer wear etc. and the oil wear are measured. or directly or indirectly, the bearing or tooth flank wear is measured. Use according to the preamble of claim 5, characterized in that preventive maintenance measures are indicated long before preventive repairs via the measured electrical conductivity and / or the change in the electrical conductivity and / or the measured dielectric constant and / or the change in the dielectric constant. Use according to the preamble of claim 5, characterized in that, through the dielectric constant and / or the change in the dielectric constant, the water content of the oil is measured and / or by the change in the dielectric constant and / or the change in the electrical conductivity, the degradation of additives is measured. Use according to the preamble of claim 5, characterized in that the volume between the electrode plates in the base sensor is the butter film in a bearing to be monitored or the lubrication film between tooth flanks on gears. Use according to claim 9, characterized in that the lubricating film thickness is further or alternatively measured. Method according to any one of claims 1 to 3, characterized by an adaptive, self-learning temperature compensation. Method according to any one of claims 1 to 3, characterized in that the measurement signals, via a serial interface, a bus system and / or a LAN or WLAN interface, are sent to a preferably web-based monitoring system. Method according to any one of claims 1 to 3, characterized by a web-based monitoring system. Use according to the preamble of claim 5, characterized in that the sensor system is used for direct moisture measurement also for aggressive and / or corrosive gases. Use according to the preamble of claim 5, characterized by use as a fuel sensor for multifuel vessels and / or machines. Use according to the preamble of claim 5, characterized by use as a crude oil sensor for measuring parameters of crude oils and their by-products. Use according to the preamble of claim 5, characterized by the measurement of crude oil constituents, such as mechanical dirt, salts, acids, water, oil-forming oil, etc., via measurements of the electrical conductivity and the dielectric constant of the crude oil.